This invention relates to phonograph cartridges, phonograph tone arms, the alignment of such cartridges on such tone arms, and more particularly, to phonograph cartridge alignment gauges and methods of phonograph cartridge alignment.
A currently common phonograph for the reproduction of sound includes, in part, a phonograph record, a turntable, a stylus and cartridge assembly, and a tone arm. The turntable has a rotary platter with a central spindle for the mounting of phonograph records. The stylus and cartridge assembly has a cantilevered stylus removably mounted on the cartridge and electromagnetic components for (i) sensing fluctuations in the spiral groove traced upon the record and (ii) converting the sensations into a correspondingly-fluctuating electrical signal, from which sound can be generated electronically. The tone arm is elongated, pivotally mounted on the turntable adjacent the platter and has a headshell for mounting of the stylus and cartridge assembly on the tone arm.
It is generally accepted that for best sound quality in such a system, the cartridge and stylus assembly must be mounted on the tone arm to minimize weighted lateral tracking error. Such error varies with the distance or "radius" of the cartridge from the spindle. At any one distance, weighted lateral tracking error equals angular error divided by the distance. Current wisdom based on H. G. Baerwald, "Analytic Treatment of Tracking Error and Notes on Optimal Pick-Up Design," Journal of the Society of Motion Picture Engineers, Vol 37, pp. 591-622, Dec. 1941, is that weighted lateral tracking error is minimized if the cartridge is mounted such that its stylus is tangent to the record groove of a turntable-mounted phonograph record at the following two distances from the spindle: 2.60 inches (66.04 mm) and 4.76 inches (120.90 mm).
However, mounting the cartridge to minimize weighted lateral tracking error is difficult, and has even been called tricky. Some physical aids to cartridge mounting have been disclosed, but all known prior art devices are either quite expensive, or difficult to use, or both. Such devices are most often difficult to use because they require multiple adjustments of their parts and the cartridge on the tone arm, and to accomodate a given tone arm pivot-to-spindle distance, visual sighting of the stylus.